1. Field
The present disclosure relates to techniques for fabricating microspring connectors. More specifically, the present disclosure relates to techniques for fabricating microsprings on non-planar surfaces.
2. Related Art
As integrated-circuit (IC) technology continues to scale to smaller critical dimensions, it is increasingly difficult for existing inter-chip connections to provide desired characteristics, such as: high bandwidth, low power, reliability and low cost. Several technologies have been proposed to address this problem, including: proximity communication or PxC (for example, with capacitive inter-chip contacts), inter-chip microsprings (with conductive inter-chip contacts), and a combination of PxC with microsprings (with capacitive inter-chip contacts). However, these proposed techniques often introduce additional packaging and reliability challenges.
PxC based on capacitive inter-chip contacts provides dense inter-chip connections, with a pitch between neighboring pads on the order of 10-100 μm. However, PxC typically requires a similar order of mechanical alignment. It can be difficult to maintain this alignment in the presence of vibrations and thermal stress using a low-cost chip package. Furthermore, the capacitance of the inter-chip contacts can be small, which makes it challenging to couple high-capacity power supplies using PxC.
Microsprings can be fabricated on a wide variety of surfaces, including: printed circuit boards (PCBs), organic or ceramic IC packages or on the surface of ICs themselves. They can be fabricated with an areal density of inter-chip connections that exceeds the density of input/output (I/O) signals on high performance ICs, and can provide electrical contacts without the use of solder. Moreover, microsprings can be designed to have more compliance than is possible by using PxC alone, which increases tolerance to mechanical movement and misalignment. Consequently, it may be useful to combine PxC with microsprings.
However, chips that communicate via PxC often include contacts on non-planar surfaces. While microsprings can be readily fabricated on a planar surface (such as the face of a silicon wafer) using existing integrated-circuit fabrication techniques, it can be difficult to fabricate microsprings on non-planar, multi-level surfaces.
Hence, what is needed is a low-cost and reliable technique for fabricating microsprings on non-planar surfaces.